I recently bought a new Deering Boston banjo and am seeking advice on what kind of 5th string capo to install, spikes or the sliding type.
This is a good question. There are advantages and disadvantages to both solutions.
Cost: Spikes are cheaper for materials and probably installation too. The 5th string capo of choice, made by Shubb, is perhaps $40 or higher these days.
Convenience of use: To me the Shubb is more convenient, as the capo lever slides into position and tightens right down next to the fret, without getting the string out of tune. Most arrangements with spikes pull the string out of its path, requiring additional tuning, and retuning once you are done using the spike.
Playability: Spikes are easier, as when fretting the 5th string with the thumb (up the neck) the Shubb adds a little width to the neck, a bit of an obstacle, but people get used to it.
Defacing the instrument: Most people prefer the small holes for the spikes in the fingerboard to the larger holes in the finished side of the neck required by Shubb installation. Additionally, the Shubb covers the dots on the side of the neck, making it harder to read them.
For me, the convenience of use/accurate tuning issue trumps all the others. As a professional, I highly value anything that reduces tuning time and increases reliability. In Masters of the Five String book, the players we asked seemed to favor the spikes by a clear majority.
I hope this helps! Good luck with your picking,